In the past, a radar apparatus that transmits and receives a continuous wave (a radar wave) to detect a target is mounted on an automobile. In the radar apparatus of this type (a vehicle-mounted radar apparatus), to detect a direction in which a target (e.g., a roadside object such as a guardrail or a leading vehicle) is present and accurately specify a position of the target, an array antenna configured by arranging a plurality of antenna elements at equal intervals specified in advance is used as a reception antenna (see, for example, Patent Literature 1).